An old bug is still there -- but now I don't think it's truly an iPhoto bug (the iPhoto glitch is the meaningless error message). See my other blog postings on this topic!
The "not enough disk space" iPhoto bug has cursed many of us over the years. This is the misleading error message iPhoto produces when something goes wrong during image exporting to the file system or to a client application (Quicktime moviews, etc). (Usually there are GBs free and the export size is a few hundred MB.)
It just means "Something has gone wrong, I don't know what".
iPhoto 4.01 was thought to have fixed this problem, but it just recurred in a new iPhoto 4.01 album of mine that contains only a few hundred images.
There are several workarounds that are thought to help [1].
In the past I've used the approach of dividing up the image set into smaller and smaller exports, until I find the one image (it's always been one image) that causes the problem. I then crop it and undo the crop and the problem resolves.
This time I tried the approach of deleting the "thumb" files in the iPhoto Library (see [1]). It didn't work.
Based on the theory that the most common cause is corruption in an iPhoto cache, I tried out the $10 Panther Cache Cleaner's "deep clean" option and rebooted. The problem resolved.
In the past I've blamed iPhoto for this problem. Now I suspect it's a deeper problem with OS X that just shows up more often in iPhoto because of its heavy use of the OS X caching subsystem. Power user forums, such as OS X Hints, now consider cleaning the cache subsystem to be the modern equivalent of rebuilding the Classic desktop -- the first solution to most problems (even before repairing privileges, which in 10.3.3 seems to rarely make a difference).
A cache subsystem problem may represent trouble in the cache code itself or in the underlying OS. There are lots of nasty interacting layers down there, where BSD Unix meets OS X. I wonder if tracking down those nasty problems is part of the task assigned the file system gurus that came to Apple from BeOS.
This is an annoying problem from iPhoto, but in my experience either tracking down the bad image or using deep cache cleaner will fix it for a while. It may, however, be a bigger problem for the OS.
[1] http://discussions.info.apple.com/WebX?128@6.XeoZaJQWlc5.8@.688eb0a2
lists many of the theoretical solutions.
